1. Technical Field
The present invention relates to a nozzle ejection amount correcting method for functional liquid which is ejected from a nozzle of an ejection head, a functional liquid ejecting method using the nozzle ejection amount correcting method, and an organic electroluminescence (EL) device manufacturing method.
2. Related Art
In the related art, a liquid droplet ejecting method (ink jet method), in which liquid droplets in a form of liquid including a functional material are ejected from a nozzle of an ink jet head and a thin film is formed, has been known. Representative examples of the thin film formed by the liquid droplet ejecting method include a color filter and a light emitting layer of an organic EL panel.
The ink jet head includes a plurality of cavities for retaining a substance in a liquid form, a plurality of nozzles which communicate with the cavities and are aligned in one direction, and a plurality of actuators (piezoelectric elements, resistive heating elements, and the like) for pressurizing the substance in a liquid form in each cavity.
The ink jet head inputs common driving signals to actuators selected based on image depiction data and causes nozzles corresponding to the respective actuators to eject liquid droplets in a liquid form. According to the ink jet method, a thin film is formed by causing the nozzles of the ink jet head to eject liquid droplets in a liquid form toward a substrate and drying the liquid droplets landed on the substrate.
It is desired to depict an image with more excellent gradation expression by the ink jet method as resolution for depicting the targeted image increases. For example, JP-A-2008-136927 discloses a method of driving a liquid droplet ejection head as an ink jet head capable of depicting an image with excellent gradation expression.
According to the method of driving a liquid droplet ejection head disclosed in JP-A-2008-136927, a plurality of different driving signals corresponding to ranks set by actuators are applied to nozzles selected based on image depiction data, and an average weight of the ejected liquid droplets can be adjusted to a predetermined weight which is defined in advance. Accordingly, it is possible to calibrate a total weight of the substance in a liquid form (liquid droplets) to be ejected on a target for each nozzle based on a combination of driving signals generated for each rank and to thereby enhance uniformity of thickness of a thin film which is obtained by drying the substance in a liquid form. Furthermore, there is a description that it is possible to further enhance precision when the average weight is adjusted and to increase a degree of freedom due to the combination of the different driving signals as compared with a case where a single driving signal is used to cause the nozzles to eject the liquid droplets.
On the other hand, since ranking gradations are limited in the method of driving a liquid droplet ejection head disclosed in JP-A-2008-136927, in which the average weight of a plurality of liquid droplets is classified into a corresponding rank, it is possible to sufficiently correct variations in weights of the liquid droplets.
In a case where variations in weights of the liquid droplets are not sufficiently corrected, liquid droplets with high weights or liquid droplets with low weights are successively aligned along a scanning direction of a substrate. For this reason, there is a problem that there is a difference in thicknesses of the thin film such as a color filter or a light emitting layer of an organic EL panel even if the weight difference between the liquid droplets with high weights and the liquid droplets with low weights is a minute difference, that the difference in film thicknesses is reflected at high sensitivity in display of an electric optical device, and that image quality is thus degraded.
As a method for solving such a problem, JP-A-2012-209216 discloses a nozzle ejection amount correcting method. The nozzle ejection amount correcting method disclosed in JP-A-2012-209216 includes: a first step for performing correction calculation in units of a first nozzle array, in units of ejection, or in units of scanning for each nozzle based on a difference between a sum A of weights of all droplets ejected to an ejecting region in a case where a weight of the liquid droplets is not corrected for each nozzle and a predetermined amount B which is set in advance, such that a sum C of the weight of the liquid droplets after correction in units of the first nozzle array, in units of ejection, or in units of scanning and a weight of liquid droplets ejected to the same ejecting region in units of nozzle arrays other than the first nozzle array, in units of ejection, or in units of scanning is equal to the predetermined amount B; and a second process for performing correction calculation in units of a second nozzle array, in units of ejection, or in units of scanning for each nozzle based on a difference between a sum D of a weight of all droplets calculated to be ejected to the ejecting region, which is corrected in the first process, and the predetermined amount B, such that a sum E of the weight of liquid droplets after correction in units of the first nozzle array, in units of ejection, or in units of scanning, a weight of liquid droplets, which are ejected to the same ejecting regions, after the correction, in units of the second nozzle array, in units of ejection, or in units of scanning, and a weight of the liquid droplets which are ejected to the same ejecting regions in units of nozzle arrays other than the first and second nozzle arrays, in units of ejection, or in units of scanning is equal to the predetermined amount B, in which correction amount calculation by the number of units of nozzle arrays, the number of units of ejection, or the number of units of scanning is performed in a stepwise manner.
According to the method disclosed in JP-A-2012-209216, it is possible to raise correction gradations by a power of the number of units of the nozzle arrays which eject liquid droplets to the ejecting region, the number of units of ejection, or the number of units of scanning since correction is performed in units of one nozzle array, in units of ejection, or in units of scanning such that the sums A and C of the weight of all the liquid droplets in the ejecting region is equal to the predetermined amount B. In doing so, it is possible to sufficiently correct variations in weights of liquid droplets ejected from the respective nozzles and to thereby uniformize the thickness of the thin film formed in the ejecting region by using the plurality of nozzles.
However, there is a concern that in a case where the driving signals applied to the respective nozzles by the actuator are corrected, the driving signals are corrected outside an appropriate correction range if priority is given to scanning, in which the number of liquid droplets ejected to the ejecting region is smaller than those in other scanning.
Specifically, the total weight of the substances in a liquid form ejected to the ejecting region is relatively smaller in scanning, in which the number of ejected liquid droplets is smaller, than those in other scanning, and if priority is given to correcting the total weight, then there is a problem that correction is performed outside an appropriate range of a standard curve which represents a relationship between setting of driving signals applied by the actuator and a weight of liquid droplets ejected from a nozzle corresponding to the actuator.